fix: do not advertise 2024-11-05 from Streamable HTTP providers

McpStreamableServerTransportProvider inherited the default
protocolVersions() from McpServerTransportProviderBase, which includes
2024-11-05. Streamable HTTP was introduced in 2025-03-26, so a provider
of this transport advertised a version whose transport it cannot serve.

Override protocolVersions() on the interface rather than on the servlet
implementation so every current and future Streamable HTTP provider is
covered, mirroring the existing McpStatelessServerTransport default.

Fixes gh-750

Author: senor14

mcp-core/src/main/java/io/modelcontextprotocol/spec/McpStreamableServerTransportProvider.java

@@ -4,6 +4,8 @@
 
 package io.modelcontextprotocol.spec;
 
+import java.util.List;
+
 import reactor.core.publisher.Mono;
 
 /**
@@ -66,4 +68,16 @@ default void close() {
 	 */
 	Mono<Void> closeGracefully();
 
+	/**
+	 * Streamable HTTP was introduced in protocol version {@code 2025-03-26}, so providers
+	 * of this transport cannot serve {@code 2024-11-05} clients and must not advertise
+	 * that version.
+	 * @return the protocol versions supported by Streamable HTTP transport providers
+	 */
+	@Override
+	default List<String> protocolVersions() {
+		return List.of(ProtocolVersions.MCP_2025_03_26, ProtocolVersions.MCP_2025_06_18,
+				ProtocolVersions.MCP_2025_11_25);
+	}
+
 }

mcp-core/src/test/java/io/modelcontextprotocol/spec/ServerTransportProtocolVersionsTests.java

@@ -0,0 +1,81 @@
+/*
+ * Copyright 2024-2025 the original author or authors.
+ */
+
+package io.modelcontextprotocol.spec;
+
+import java.util.List;
+
+import io.modelcontextprotocol.server.McpStatelessServerHandler;
+import org.junit.jupiter.api.Test;
+import reactor.core.publisher.Mono;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Verifies that each server transport abstraction advertises only the protocol versions
+ * it can actually serve.
+ */
+class ServerTransportProtocolVersionsTests {
+
+	private static final List<String> STREAMABLE_HTTP_VERSIONS = List.of(ProtocolVersions.MCP_2025_03_26,
+			ProtocolVersions.MCP_2025_06_18, ProtocolVersions.MCP_2025_11_25);
+
+	private static final McpStreamableServerTransportProvider STREAMABLE_PROVIDER = new McpStreamableServerTransportProvider() {
+		@Override
+		public void setSessionFactory(McpStreamableServerSession.Factory sessionFactory) {
+		}
+
+		@Override
+		public Mono<Void> notifyClients(String method, Object params) {
+			return Mono.empty();
+		}
+
+		@Override
+		public Mono<Void> closeGracefully() {
+			return Mono.empty();
+		}
+	};
+
+	private static final McpStatelessServerTransport STATELESS_TRANSPORT = new McpStatelessServerTransport() {
+		@Override
+		public void setMcpHandler(McpStatelessServerHandler mcpHandler) {
+		}
+
+		@Override
+		public Mono<Void> closeGracefully() {
+			return Mono.empty();
+		}
+	};
+
+	@Test
+	void streamableProviderDoesNotAdvertiseVersionsPredatingStreamableHttp() {
+		assertThat(STREAMABLE_PROVIDER.protocolVersions()).doesNotContain(ProtocolVersions.MCP_2024_11_05)
+			.containsExactlyElementsOf(STREAMABLE_HTTP_VERSIONS);
+	}
+
+	@Test
+	void statelessTransportDoesNotAdvertiseVersionsPredatingStreamableHttp() {
+		assertThat(STATELESS_TRANSPORT.protocolVersions()).doesNotContain(ProtocolVersions.MCP_2024_11_05)
+			.containsExactlyElementsOf(STREAMABLE_HTTP_VERSIONS);
+	}
+
+	@Test
+	void transportsWithoutStreamableHttpConstraintKeepTheFullRange() {
+		McpServerTransportProviderBase base = new McpServerTransportProviderBase() {
+			@Override
+			public Mono<Void> notifyClients(String method, Object params) {
+				return Mono.empty();
+			}
+
+			@Override
+			public Mono<Void> closeGracefully() {
+				return Mono.empty();
+			}
+		};
+
+		assertThat(base.protocolVersions()).containsExactly(ProtocolVersions.MCP_2024_11_05,
+				ProtocolVersions.MCP_2025_03_26, ProtocolVersions.MCP_2025_06_18, ProtocolVersions.MCP_2025_11_25);
+	}
+
+}